Atom interferometry is used to provide sensitive measurements of inertial forces for inertial navigation and geophysical applications. At present, state of the art atom interferometer inertial sensors involve light pulses rather than mechanical gratings for coherent manipulation of matter waves. Many implementations of light pulse atom interferometers use stimulated Raman transitions as the atom beamsplitter and minor. While other light pulse beamsplitters, such as multi-photon Bragg pulses and Bloch oscillations, may achieve larger momentum transfer and thus offer higher interferometer sensitivity, Raman pulse beamsplitters are relatively simple to implement and place less stringent requirements on atom temperature and laser power.
Referring to FIG. 1, in a Raman pulse beamsplitter, a bichromatic (two frequencies) laser field 110 drives stimulated Raman transitions in cold atoms 120. The laser field affects the population distribution of the cold atoms, and allows effects of interest to be measured. Atom interferometry relies on the presence of known initial conditions, specifically, a polarized atom cloud. Optical pumping is used to create polarized atom samples, and Raman pulses may be applied to such polarizations to create atomic coherences. However, the phase of the resulting coherence can deviate from the phase of the drive field in an uncontrolled fashion, because of frequency tuning error of the drive, AC Stark shifts of the atomic resonance, or other spurious resonance shifts.